The present invention relates to a printing method and apparatus and, more particularly to a printing method and apparatus using an ink-jet printing method, which performs printing by discharging ink droplets from printhead nozzles, based on image information, on a recording medium.
Conventionally, ink-jet type printers perform image formation by discharging ink droplets from a plurality of nozzles (orifices) of a printhead, based on image information, on a recording medium. In the present invention hereinafter, xe2x80x9cimagexe2x80x9d is defined as involving not only a usual image but also characters and symbols. The printhead typically has a plurality of nozzles connected to a plurality of orifices, a liquid chamber commonly connected to the nozzles and an ink tank which supplies ink to the chamber. The nozzles respectively have a heater as a thermal-energy generating means for heating ink to form bubbles and discharging ink as droplets from the orifice.
In the printhead having the above construction, when forming bubbles in ink on or above the heater due to heating, dissolved air in the ink becomes air bubbles. If printing time is long, the air bubbles remain within the liquid chamber, and in some cases, disturb ink-supply to the nozzles. There is a tendency that the air bubbles occur at a high temperature, and cause failure of ink-discharge in a printing operation.
To prevent such ink-discharge failure, conventional ink-jet printers have operated an air-suction pump to suck air bubbles and forcibly discharge the bubbles to the outside of the nozzles, typically using the following suction operations:
(1) Suction operation automatically performed upon installation of the printhead to a printer;
(2) Automatic suction operation periodically performed if printing is not performed for a long time. To avoid increase of ink viscosity and ink-stick to the orifices, suction is performed periodically in accordance with the length of a non-printing period, made as disclosed in Japanese Patent Application Laid-Open Nos. 60-2368 and 63-193846; and
(3) Manual suction operation in accordance with the user""s decision. This is made where excellent image quality cannot be obtained due to failure of ink-discharge.
However, in the case of a long printing time, these suction operations cannot prevent completely discharge failure of ink droplets caused by air bubbles in the printhead.
Accordingly, it is an object of the present invention to provide a printing method for obtaining excellent image quality even in case of long printing time, without failure of ink discharge.
According to the present invention, the foregoing object is attained by providing a printing method for performing printing on a recording medium, using an ink jet printhead, comprising a suction step of performing recovery suction on nozzles of the printhead, a recording step of performing image recording by discharging ink from the printhead, based on an input image signal, on the recording medium, a counting step of counting a number of ink droplets discharged from the printhead or a representative value of the ink droplets, an accumulation step of accumulating the number of ink droplets or the representative value, from a point where the recovery suction has been done, a comparison step of comparing the number of ink droplets or the representative value, accumulated in said accumulation step, with a predetermined threshold value, and a control step of controlling the recovery suction, based on the result from comparison in said comparison step.
It is another object of the present invention to provide a printing apparatus that obtains excellent image quality even in the case of a long printing time, without failure of ink discharge.
According to the present invention, the foregoing object is attained by providing a printing apparatus which performs printing on a recording medium, using an ink jet printhead, comprising suction means for performing recovery suction on nozzles of the printhead, recording means for performing image recording by discharging ink from the printhead, based on an input image signal, on the recording medium, counting means for counting a number of ink droplets discharged from the printhead or a representative value of the ink droplets, accumulation means for accumulating the number of ink droplets or the representative value, from a point where the recovery suction has been done, comparison means for comparing the number of ink droplets or the representative value, accumulated by said accumulation means, with a predetermined threshold value, and control means for controlling the recovery suction, based on the result from comparison by said comparison means.
In accordance with the present invention as described above, the number of ink droplets discharged from the printhead or a representative number of the ink droplets is counted. The counted number of ink droplets or the representative number is accumulated from a point where suction operation has been performed. Then the accumulated value is compared with a predetermined threshold, and in accordance with the comparison result, recovery suction is performed on the printhead nozzles.
The invention is particularly advantageous since the recovery suction can be performed on the printhead nozzles in correspondence with status of use of the printhead. This construction enables recovery suction at an appropriate point in long printing operation, thus avoids failure ink-discharge and can maintain excellent image printing.